1. Field of the Invention
The present invention relates to a composition for solubilizing a poorly soluble substance in water and a method for solubilizing a poorly soluble substance in water by using the composition.
2. Description of the Related Art
Methods for solubilizing poorly soluble substances in water are currently being developed by many researchers in the cosmetic and pharmaceutical industries. It is expected that such techniques for solubilizing poorly soluble substances will be further developed in the future because of their significant ripple effects in the industry.
Poorly soluble hydrophobic substances have few or no hydrophilic groups or have hydrophilic groups at positions where their molecular arrangements are disturbed. The strong intermolecular hydrophobic interactions result in the formation of molecular arrangements that make it difficult to solubilize the hydrophobic substances in water. Any deformation of the molecular arrangements of the hydrophobic substances may make the poorly soluble substances dispersible or soluble. Substances capable of inducing changes in molecular arrangement are called surfactants.
A wide variety of surfactants have proven their usefulness in the cosmetic and pharmaceutical industries. Techniques have been developed for producing nanoparticles of poorly soluble substances using synthetic and natural surfactants under physical conditions created by suitable devices, such as ultra-homogenizers. However, the conventional techniques have limitations in solubilizing poorly soluble substances at high concentrations and stabilizing the solubilized substances. Thus, there has been an increasing demand for the development of new natural soluble substances and new solubilization systems.
Ceramides are well known as poorly soluble substances in the cosmetic industry. Ceramides are representative structural components of the skin that reinforce the barrier function of the skin. Human skin possesses various ceramides. Ceramides exhibit strong hydrophobic interactions in the skin due to the presence of a relatively small number of hydrophilic groups. Such structural features allow ceramides to exhibit their inherent skin barrier functions of preventing moisture loss from the human body and blocking the ingress of harmful ingredients from the external environment through the skin. Therefore, the application of ceramides to cosmetics increases the moisturizing power of the cosmetics and greatly enhances the skin-protecting power of the cosmetics, contributing to a considerable improvement in the quality of the cosmetics.
However, currently commercially available ceramides tend to aggregate in cosmetic formulations owing to high hydrophobic interactions between their molecular chains and hence possess serious disadvantages in that they are precipitated as needle-like crystals.
Solubilization of hydrophobic poorly soluble substances, such as rutein, resveratrol, phylloquinone, ubiquinone, oleanolic acid, bis-ethylhexyloxyphenol triazine, astaxanthin, rutin, hesperidin, and chloramphenicol, is considered a very important technical task in the cosmetic and pharmaceutical industries. Development of techniques for the solubilization of these hydrophobic poorly soluble substances is a crucial factor in maximizing the efficacy of the active ingredients and improving the quality of final products. In view of this situation, a strong need exists to develop new solubilization techniques.
Many researchers have made efforts to solve the above problems based on self-aggregation techniques and solubilization techniques. Despite such efforts, these techniques can be used at very limited concentrations in the current state of the art.
In most of such solubilization systems, phospholipids (e.g., phosphatidylcholine (lecithin)) as natural surfactants are currently in use. However, phospholipids are irregular in structure and have characteristic hydrophobic groups, limiting their use as solubilization substances. Particularly, phospholipids per se cannot be formed into small particles and have a limitation in that their particle size can be reduced to the micrometer or nanometer level only under high pressure.
Thus, there is a need to develop solubilization systems capable of solubilizing and stabilizing hydrophobic poorly soluble substances. Furthermore, there is an urgent need for the development of new materials that can form hydrophobic poorly soluble substances into nanoparticles without the need for physical pressure.